Tris(mercaptoalkyl) cyclohexanes

ABSTRACT

Tristhioalkanoates illustrated by S,S,S-(2,2,2-(1,2,4cyclohexanetriyl)trisethyl)tristhioacetate and S,S,S-(2,2,2(1,3,5-cyclohexanetriyl)trisethyl)tristhioacetate having utility as intermediates for the production of tris(mercaptoalkyl)cyclohexanes illustrated by 1,2,4-tris(2mercaptoethyl)cyclohexane and 1,3,5-tris(2mercaptoethyl)cyclohexane, which have utility as cross-linking agents for polythiols and polyepoxides which in turn are useful as adhesives and coatings upon curing.

United States Patent Inventors Faber B. Jones Bartlesvllle, 0kla.;

Jack E. Reece, Wlllernie, Minn.

Dec. 18, 1969 Nov. 30, I97] Phillipa Petroleum CompanyContinuation-impart of application Ser. No. 675,054, Oct. 13, 1967, nowPatent No. 3,505,166, dated Apr. 7, 1970. This application Dec. 18,1969, Ser. No. 886,377

App]. No. Filed Patented Assignee TRISOHERCAPTOALKYL) C YCLOHEXANES 1Claim, No Drawings [50] Field of Search 260/609 D [56] Reierences CitedFOREIGN PATENTS 43/2 14 I 5 I968 Japan 260/609 E PrimaryExaminer-Charles B. Parker Assistant Examiner-D. R. PhillipsAttorney-Young and Quigg ABSTRACT: Tristhioalkanoates illustrated byS,S,S-{2,2,2- (l,2,4-cyclohexanetriyl)trisethylltristhioacetate and8,8,8- [2,2,2-( 1,3 ,S-cyclohexanetriyl )trisethyl]tristhioacetatehaving utility as intermediates for the production oftris(mercaptoalkyl)cyclohexanes illustrated by l,2,4-tris(2-mercaptoethyl )cyclohexane and l ,3 ,5-tris(Z-mercaptoethyhcyclohexane, which have utility as cross-linking agentsfor polythiols and polyepoxides which in turn are useful as adhesivesand coatings upon curing.

TRIS(MERCAPI"ALKYL) CYCLOI'IEXANES This application is acontinuation-impart application of our copending application having Ser.No. 675,054 filed Oct. 13, 1967 now U.S. Pat. No. 3,505,166.

BACKGROUND OF THE INVENTION The direct synthesis of organic sulfurcompounds, especially thiols and sulfides (thioethers), by the additionof hydrogen sulfide or thiols to olefinic materials, with or without thepresence of a catalyst, has been reported by various investigators.However, there is a continued research effort being directed to theproduction of new thiols and better processes for producing thesematerials.

This invention relates to new compositions of matter and to processesfor producing these new compositions of matter. In one aspect, thisinvention relates to novel cyclic polythiols comprisingtris(mercaptoalkyl)cyclohexanes. In another aspect, this inventionrelates to new compounds, l,2,4-tris(2- mercaptoethyl )cyclohexane and1,3 ,5-tris( 2-mercaptoethyl)cyclohexane, derived fromtrivinylcyclohexanes. In another aspect, this invention relates to thepreparation of polythiols from trivinylcyclohexanes by first formingnovel tristhioalkanoates as intermediates. In a further aspect, thisinvention relates to the curing of polyepoxides using novel cyclicpolythiols as curing agents. In accordance with a still further aspect,this invention relates to novel tristhioalkanoates produced fromtrivinylcyclohexanes and thioalkanoic acids. In another aspect, thisinvention relates to new compositions S,S,S-[2,2,2-(l,2,4-cyclohexanetriyl)- trisethylltristhioalkanoates and S,S,S-[2,2,2-(l ,3,5-cyclohexanetriyl)-trisethylltristhioalkanoates derived fromtrivinylcyclohexanes. In a further aspect, this invention relates to newcompounds S,S,S-[2,2,2-( l ,2,4-cyclohexanetriyl)trisethyl]tristhioacetate and S,S,S-[2,2,2-( l,3,5-cyclohexanetriyl)trisethyl1tristhioacetate.

Accordingly, an object of this invention is to provide novel thiols.

Another object of this invention is to provide novel tristhioalkanoates.

Another object of this invention is to provide a commercially feasibleprocess for the preparation of cyclic polythiols.

A further object of this invention is to provide a process for thepreparation of novel tristhioalkanoates.

Other aspects and objects, as well as the several advantages of thisinvention, will be apparent to those skilled in the art from a study ofthe specification and the appended claims.

SUMMARY OF THE INVENTION According to the invention, cyclohexanescontaining at least three hydrocarbon substituents having olefinicunsaturation are converted to novel tris(mercaptoalkyl)cyclohexanes.

Further according to the invention, cyclohexanes containing at leastthree hydrocarbon substituents having olefinic unsaturation areconverted to novel tristhioalkanoates by reaction with thioalkanoicacids.

Further according to the invention, trivinylcyclohexanes are convertedto novel tris(mercaptoethyl)cyclohexanes by first reacting thetrivinylcyclohexanes with thioalkanoic acids to producetristhioalkanoates as intermediates which are saponified, either incrude form or refined form, to form the novel tris( mercaptoethyl)cyclohexanes.

More specifically, trivinylcyclohexane, either 1,3,5-trivinylcyclohexaneor l,2,4-trivinylcyclohexane, is reacted with a thioalkanoic acid toform S,S,S-]2,2,2-( l,2,4-cyclohexanetriyl)-trisethylltristhioalkanoatesor S,S,S-[2,2,2-(l,3,5- cyclohexanetriyl)-trisethylltristhioalkanoates.The thusformed tristhioalkanoates can be saponified as a crude reactionproduct or the tristhioalkanoates can be isolated prior tosaponification to form the novel tris(mercaptoethyl)cyclohexanes,

Specific novel tris(mercaptoalkyhcyclohexane compounds producedaccording to the invention are: l,2,4-tris(2-mercaptoethyl )cyclohexaneand l,3 ,5-tris( Z-mercaptoethyl )cyclohexane.

0 hesives or sealants.

PREFERRED EMBODIMENTS OF THE INVENTION The novel cyclic polythiols ofthe invention can be prepared by procedures known in the art. Thetrivinylcyclohexanes, which are preferred starting materials forproducing the novel cyclic polythiols of the invention, can be formed bypyrolysis of 1,5,9-cyclododecatriene. The conversion of l,5,9-cyclododecatriene at elevated temperature, and optionally in thepresence of a catalyst, results in the formation of thetrivinylcyclohexane compound, as is disclosed by U.S. Pat. No. 3,011,003and British Pat. No. 848,637. The trivinylcyclohexanes thus produced canbe converted to a novel tris(mercaptoethyl)cyclohexane of the inventionby reaction with I-I,S in the presence of a free radical initiator, byfree radical addition of an alkylthiol (such as methyl or ethyl thiol)to the trivinylcyclohexane with subsequent cleavage of the thus-formedtrisulfide with H S in an acidic environment, or by the addition of athioalkanoic acid in the absence or presence of a free radical initiatorwith subsequent saponification of the tristhioalkanoate.

The novel tris(mercaptoethyl)cyclohexane products of this invention arepreferably prepared by the addition of a thioalkanoic acid to thetrivinylcyclohexane starting material with 5 subsequent saponificationof the thus-formed tristhioalkanoate. Thioacetic acid is preferablyemployed, though thioalkanoic acids having as many as six carbon atomscan be employed.

The tristhioalkanoates are prepared by reaction of a trivinylcyclohexanewith a thioalkanoic acid as disclosed by the following representation:

I i cupcake-041 I wherein the vinyl or ethyl thioalkanoate groups arepositioned in the l, 3, 5 or I, 2, 4 positions of the cyclohexane ring,and wherein R is an alkyl group having in the range of one to fivecarbon atoms per alkyl group.

The novel tristhioalkanoates of the invention can be defined as newcompositions S, S, S-[2,2,2-( l,2,4'cyclohexanetriyl)-trisethyl]tristhioalkanoates and S,S,S-[2,2,2-(l,3,5-cyclohexanetriyl)-trisethyl)tristhioalkanoates wherein thethioalkanoate moieties thereof can have in the range of one to sixcarbon atoms per thioalkanoate moiety. Examples of new compositionsfalling within the generic definition include the following:

S,S,S-l 2,2,2-( l,2,4-cyclohexanetriyl)trisethyl] tristhioacetateS,S,S-[2,2,2-( l ,3,5-cyclohexanetriyl )trisethyl] tristhioacetateS,S,S-[ 2,2,2-( l,2,4-cyclohexanetriyl )trisethyl1tristhiohexanoateemployed as a starting material rather than the 1,2,4-trivinyll0cyclohexane. For example,S,S,S-[2,2,2-(1,2,4-cyclohexanetriyl)trisethylltristhioacetate isproduced by the reaction of 1,2,4-trivinylcyclohexane with thioaceticacid whereas S,S,S-[2,2,2-(l,3,5-cyclohexanetriyl)trisethyl1tristhioacetate is produced by thereaction of l,3,5-trivinylcyclohexane with thioacetic acid.

Generally in the range I to 20 moles of thioalkanoic acid for each moleof trivinylcyclohexane are employed, preferably in the range of 3 tomoles of thioalkanoic acid per mole of trivinylcyclohexane are employed.Temperatures in the range of 0 to 200 C. are employed, preferably thetemperature is in the range of 40 C. to 150 C. sufficient time to effectthe desired degree of conversion should be used, generally reactiontimes in the range of 5 minutes to 24 hours are suitable. Though eithersuperatmospheric or subatmospheric pressure can be employed, atmosphericpressure is normally used because of convenience.

The novel tristhioalkanoates produced can be recovered as stablecompounds utilizing any means known to be suitable for the recovery ofesters. For example, such recovery techniques as solvent extraction,removal of volatiles with heat, selective precipitation, and the likecan be employed. However, if desired, the tristhioalkanoates need not berecovered prior to saponification, but can be saponified using a crudereaction product.

Saponification of the novel tristhioalkanoate intermediate products iseffected by contacting that product,,either with or without separationfrom the other materials present, with alkaline material such as NaOH,KOH, LiOH, or the like, under conditions such that the thioesterlinkages are split to yield the novel tris( mercaptoethyl)cyclohexaneproducts. In general, in the range of about 3 to about 40 moles ofalkali per mole of tristhioalkanoate are employed. The temperature canrange from about 40 C. to the decomposition temperature of the product;generally, the temperature is preferably in the range of about 50 C. tothe reflux temperature of the reaction medium. Pressures that are eithersubatmospheric or superatmospheric can be employed, though atmosphericpressure is normally preferred because of convenience. Reaction timeshould be sufficient to effect the degree of saponification desired;normally, reaction times of about 30 minutes to 48 hours are suitable.Suitable diluents that are substantially nonreactive in the reactionenvironments can be employed, such as benzene, toluene, xylene, hexane,and the like. Products can be separated and purified, if desired, byordinary means known to the art such as distillation, filtration,crystallization, and the like.

Free radical agent, when utilized, can be from chemical sources, or thefree radicals can be supplied by energy sources which cause theformation of free radicals in situ. For example, peroxide compounds andorganic azo compounds can be employed as chemical sources of freeradicals, and actinic irradiation can be employed for the generation offree radicals. The terminology actinic irradiation as used hereinincludes activating rays such as ultraviolet rays having a wavelength inthe range l00-3,800 Angstroms and ionizing rays such as alpha rays, betarays, gamma rays, X-rays neutrons, and the like. The ultraviolet rayscan be supplied from lamps and the like, while the ionizing radiationcan be supplied from such sources as cathode tubes, accelerators,natural and artificial radioactive elements, spent fuel elements fromatomic reac tors, and the like. If actinic irradiation is employed, theenergy level of the irradiation will generally be in the range between2.] and 1X10 electron volts. The irradiation dose rate will generally befrom 10 to 10 rep (roentgen equivalent physical) per hour, while thetotal irradiation dosage will generally be from 10 to 10 rep. The amountof chemical free radical generating agent which can be employed can varyover a wide range, but is generally less than 5 mole percent based onthe trivinylcyclohexane.

Some specific examples of chemical free radical sources which can beused include ditert alkyl peroxides, alkyl hydroperoxides, alkyl peroxyesters, diacyl peroxides, and the like. Preferred chemical free radicalsources are the azo compounds such as alpha,alpha-azo diisobutyronitrileand others such as are disclosed in US. Pat. Nos. 2,471,959; 2,492,763;and 2,503,253.

Hydrogen sulfide employed for the reaction of the trivinylcyclohexanecan be in the liquid state if the pressure is high enough and thetemperature relatively low. The amount of hydrogen sulfide employed willvary appreciably and will generally be in the range of about 1 to I00moles of hydrogen sulfide per mole of trivinylcyclohexane. Although thehydrogen sulfide used according to the invention can be a crude product,it is often advantageous to distill the hydrogen sulfide prior toadmixing with the trivinylcyclohexane to remove dissolved free sulfur.

The addition of H 8 or alkylthiols of this invention to form thetrithiols or trisulfides can be carried out in a manner like that of theprior art and can be effected in a batch, intermittent, or continuousmanner. Diluents that are substantially completely nonreactive in thereaction environment can be employed. For example, compounds such asbenzene, toluene, xylene, hexane, dodecane, and the like can be used.Hydrogen sulfide can be passed through the trivinylcyclohexane reactantor solution until the reaction is substantially completed, for example,for a period varying from 0.5 hours to 72 hours, or more, depending uponthe conditions of reaction. Reaction temperature can vary over a widerange, and generally will range from about 50 to about 300 F. Thepressure at which the reaction is carried out will also vary, andgenerally will be sufficient to maintain liquid phase conditions,although vapor phase or mixed phase conditions are possible. Thepressure can vary from about atmospheric to about 1,000 p.s.i. g.

No special apparatus is required to carry out the reaction in accordancewith the invention. when atmospheric pressure is used, the reaction canbe carried out in an open vessel, while the reaction undersuperatmospheric pressure can be carried out in any suitable container,such as an autoclave.

It is normally preferred to exclude air from the reaction medium inorder to avoid oxidation of the trithiol or trisulfide products formed.

If trisulfides are formed by the addition of alkylthiols totrivinylcyclohexane, such trisulfides can be converted to thetris(mercaptoethyl)cyclohexane products by cleavage with H 8 in anacidic environment. Pressures in the range of IO to 1,000 p.s.i.g. i.and temperatures in the range of 20 C. to reflux temperature at thepressure used can be employed, provided that temperatures at or abovethe decomposition point of any of the materials should be avoided.

Products can be recovered by any well-known separation procedure. Forexample, gases can be recovered or released to the atmosphere, andliquids can be distilled, crystallized, or subjected to variousseparation and recovery procedures to obtain the desired tris(mercaptoalkyl)cyclohexane product.

As noted above, the novel cyclic polythiols of the present invention areparticularly useful and valuable as curing agents for polyepoxides. Thepolyepoxides that can be cured to valuable adhesives by the trithiols ofthis invention are exemplified by the glycidyl resins of FIG. 1, page167, Modern Plastics En- Cyclopedia, 1967, Volume 44No. 14. These epoxyresins, as they are known to the art, are common items of commerce and,in general, have two or more glycidyl groups per molecule. However,polyepoxides that can be cured according to the process of thisinvention include compounds within the following generic formula:

where Y is an organic group having a valence of n that can contain inthe range of two to 200 carbon atoms and, optionally, as many as 20atoms of O, S, or N, provided that the O, S, or N atoms are bonded tocarbon or atoms other than hydrogen; and where n is an integer in therange of two to 12. Examples can include: epichlorohydrin-bis phenol Aresin, epoxy-novolac resin, diglycidyl isophthalate resin, diglycidylether of dimerized linolic acid, 1,2,4,5-diepoxypentane, di(4,5-epoxypentyl)thiomaionate, and the like. 7

ln curing polyepoxides with the trithiols of this invention, it is oftenadvantageous to employ activators for the cure. Examples of theseinclude: amines, such as diethylaminopropylamine, tri-n-butyl amine,p,p-bis- (dimethylaminophenyl)methane, benzyldimethylamine,diethylenetriamine, triethylenetetraamine, dimethylaniline, and thelike; phenols; organic phosphines; sulfides; organic arsines; organicantimony compounds; and the like. Particularly preferred are tertiaryamines or compounds that are convertible to tertiary amines in situ.

Various other ingredients can be mixed with the polythiol or polyepoxidesubjected to cure with the novel tris(mercaptoalkyl)cyciohexanes of theinvention, including pigments, filler, dyes, plasticizers, resins, andthe like.

The polyepoxides, for example, can be cured with the new trithiols bymerely mixing the components together, preferably in the presence of anactivator. The cure time can vary from a few minutes to a few hours,depending on the type and quantity of reactants and presence ofcatalyst. In the presence of an activator, the cure takes place readilyat room temperature. Faster reaction can be obtained, of course, byapplying heat, e.g., in the range 30 C. to 200 C.

The trithiols of this invention are normally employed in amounts suchthat about one thiol group is provided for each epoxy group of thepolyepoxide. Of course, reasonable variation in the range of about 0.8to 1.2 moles of thiol groups per mole of epoxide groups can be used.

Synthesis of and utility for the novel tris(mercaptoethyl)cyclohexanecompounds of this invention are demonstrated by the following examples:

EXAMPLE I To a stirred reactor was charged 53 g. (0.33 mole) of 1,2,4-trivinylcyclohexane. A total of 9l g. (1.2 moles) of thioacetic acid wasthen slowly added at such rate as to maintain the temperature of thereaction mixture below 60C. The mixture was then heated to H0 C. for 30minutes and cooled to room temperature to producel,2,4-tri-(2-mercaptoethyl)cyclohexane triacetate, e.g., S,S,S-[2,2,2-(l,2,4-cyclohexanetriyl)- trisethyll To the above mixture was then added amixture comprised of 500 ml. of ethanol, 200 ml. of H 0, and 96 g. NaOH.Reflux was maintained for 3.5 hours, cooling was effected.neutralization was effected with HCl. An ether extract of the resultantmixture was washed with Water, dried over MgSO4. and evaporated todryness to yield 51.4 g. of 1.2.4-tris(2-mercaptoethyl)cyclohexaneproduct, boiling point 174 C.l85 C., 0.41.2 mm. Hg.

An infrared spectrum of the material had no bands characteristic ofthioacetate groups, but had bands characteristic of thiol groups.

EXAMPLE it To a stirred reactor were charged 1 1.16 g. of Epon 828",5.22 g. of the 1,2,4-tris(2-mercaptoethyl)cyclohexane product of exampleI, and 0.1 g. of DMP-30. The reactor contents were stirred at 25 C. andapplied to aluminum coupons for lap shear tests. Gel time was about 29minutes and tem erature rose to about C.

e lap shear tests made on the adhesive were effected in accordance withstandard procedure, ASTM designation O1002-53T. Briefly, the testconsists of placing a precleaned aluminum coupon (1.000 inch X 4.000inch X 0.064 inch) in a silicon spray coated jig and coating one end ofthe coupon with the material to be evaluated. After about lap 30 minutesthe materials to be tested have gelled sufficiently so that they willnot run off. Another coupon is placed over the first coupon in suchmanner that only a rfi-inch overlap is formed. The space between thecoupons, filled with test adhesive, is generally 5 to 10 mils thick. Thetop of the holder is placed in position, and the assembly is ready forany cure cycle desired. After cure is effected, the bonded coupons aretaken out, the excess adhesive is removed, and the mil thickness of thebond is measured. To efiect uniformity, all bonding surfaces are cleanedbefore applying adhesive. This is effected by vapor degreasing thecoupons in trichloroethylene, followed by acid etching, water washing,and oven drying. The coupons are normally used within 1 hour afterdrying.

Lap shear specimens prepared in the above manner were cured at 25 C. for16 hours, C. for 4 hours, and C. for 4 hours, to develop full adhesivestrength and effect uniformity. They were then tested to failure fortensile shear employing an lnstron Model Tl testing machine at a strainrate of 0.05 inches per minute. Tensile lap shear strength at roomtemperature, as determined in triplicate for the above adhesive, wasdetermined to be 2,857 pounds per square inch of the bond area.

1. Epon 828 is a trademark for a product characterized as a diglycidylether of his phenol A with an equivalent weight of 187 and a structurethus 2. DMP-3O is tris-2,4,6-(dimethylaminomethyl)phenol.

We claim: 1. As compounds, l,2,4-tris(Z-mercaptoethyl)cyclohexane andl,3,5-tris( l-mercaptoethyl) cyclohexane.

